libstdc++: Fix usage of __GXX_WEAK__ in TM TS support.

	* include/bits/c++config (_GLIBCXX_USE_WEAK_REF): New.
	(_GLIBCXX_TXN_SAFE, _GLIBCXX_TXN_SAFE_DYN): Use	_GLIBCXX_USE_WEAK_REF
	and move after its definition.
	* config/os/aix/os_defines.h (_GLIBCXX_USE_WEAK_REF): Override.
	* src/c++11/cow-stdexcept.cc: Use _GLIBCXX_USE_WEAK_REF instead of
	__GXX_WEAK__, and only provide transactional clones if
	_GLIBCXX_USE_WEAK_REF is true.  Don't provide stubs of libitm
	functions.

From-SVN: r232539

4 files changed, 45 insertions, 28 deletions

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 0b7ca1b..d68f5a5 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,14 @@
+2016-01-18  Torvald Riegel  <triegel@redhat.com>
+
+	* include/bits/c++config (_GLIBCXX_USE_WEAK_REF): New.
+	(_GLIBCXX_TXN_SAFE, _GLIBCXX_TXN_SAFE_DYN): Use	_GLIBCXX_USE_WEAK_REF
+	and move after its definition.
+	* config/os/aix/os_defines.h (_GLIBCXX_USE_WEAK_REF): Override.
+	* src/c++11/cow-stdexcept.cc: Use _GLIBCXX_USE_WEAK_REF instead of
+	__GXX_WEAK__, and only provide transactional clones if
+	_GLIBCXX_USE_WEAK_REF is true.  Don't provide stubs of libitm
+	functions.
+
 2016-01-18  Jonathan Wakely  <jwakely@redhat.com>
 
 	PR libstdc++/60637
diff --git a/libstdc++-v3/config/os/aix/os_defines.h b/libstdc++-v3/config/os/aix/os_defines.h
index d895471..0949446 100644
--- a/libstdc++-v3/config/os/aix/os_defines.h
+++ b/libstdc++-v3/config/os/aix/os_defines.h
@@ -48,4 +48,7 @@
 #define __COMPATMATH__
 #endif
 
+// No support for referencing weak symbols without a definition.
+#define _GLIBCXX_USE_WEAK_REF 0
+
 #endif
diff --git a/libstdc++-v3/include/bits/c++config b/libstdc++-v3/include/bits/c++config
index 387a7bb..57024e4 100644
--- a/libstdc++-v3/include/bits/c++config
+++ b/libstdc++-v3/include/bits/c++config
@@ -483,20 +483,6 @@ namespace std
 
 #define _GLIBCXX_USE_ALLOCATOR_NEW
 
-// Conditionally enable annotations for the Transactional Memory TS on C++11.
-// Most of the following conditions are due to limitations in the current
-// implementation.
-#if __cplusplus >= 201103L && _GLIBCXX_USE_CXX11_ABI			\
-  && _GLIBCXX_USE_DUAL_ABI && __cpp_transactional_memory >= 201505L	\
-  &&  !_GLIBCXX_FULLY_DYNAMIC_STRING && __GXX_WEAK__ 			\
-  && _GLIBCXX_USE_ALLOCATOR_NEW
-#define _GLIBCXX_TXN_SAFE transaction_safe
-#define _GLIBCXX_TXN_SAFE_DYN transaction_safe_dynamic
-#else
-#define _GLIBCXX_TXN_SAFE
-#define _GLIBCXX_TXN_SAFE_DYN
-#endif
-
 #else // !__cplusplus
 # define _GLIBCXX_BEGIN_EXTERN_C
 # define _GLIBCXX_END_EXTERN_C
@@ -524,6 +510,28 @@ namespace std
 # define _GLIBCXX_WEAK_DEFINITION
 #endif
 
+// By default, we assume that __GXX_WEAK__ also means that there is support
+// for declaring functions as weak while not defining such functions.  This
+// allows for referring to functions provided by other libraries (e.g.,
+// libitm) without depending on them if the respective features are not used.
+#ifndef _GLIBCXX_USE_WEAK_REF
+# define _GLIBCXX_USE_WEAK_REF __GXX_WEAK__
+#endif
+
+// Conditionally enable annotations for the Transactional Memory TS on C++11.
+// Most of the following conditions are due to limitations in the current
+// implementation.
+#if __cplusplus >= 201103L && _GLIBCXX_USE_CXX11_ABI			\
+  && _GLIBCXX_USE_DUAL_ABI && __cpp_transactional_memory >= 201505L	\
+  &&  !_GLIBCXX_FULLY_DYNAMIC_STRING && _GLIBCXX_USE_WEAK_REF		\
+  && _GLIBCXX_USE_ALLOCATOR_NEW
+#define _GLIBCXX_TXN_SAFE transaction_safe
+#define _GLIBCXX_TXN_SAFE_DYN transaction_safe_dynamic
+#else
+#define _GLIBCXX_TXN_SAFE
+#define _GLIBCXX_TXN_SAFE_DYN
+#endif
+
 
 // The remainder of the prewritten config is automatic; all the
 // user hooks are listed above.
diff --git a/libstdc++-v3/src/c++11/cow-stdexcept.cc b/libstdc++-v3/src/c++11/cow-stdexcept.cc
index eddb36b..a0f505c 100644
--- a/libstdc++-v3/src/c++11/cow-stdexcept.cc
+++ b/libstdc++-v3/src/c++11/cow-stdexcept.cc
@@ -179,6 +179,13 @@ _GLIBCXX_END_NAMESPACE_VERSION
 // Furthermore, _Rep will always have been allocated or deallocated via
 // global new or delete, so nontransactional writes we do to _Rep cannot
 // interfere with transactional accesses.
+
+// We depend on having support for referencing functions declared weak that
+// are not defined by us.  Without such support, the exceptions will not be
+// declared transaction-safe, so we just don't provide transactional clones
+// in this case.
+#if _GLIBCXX_USE_WEAK_REF
+
 extern "C" {
 
 #ifndef _GLIBCXX_MANGLE_SIZE_T
@@ -195,7 +202,6 @@ extern "C" {
 # define ITM_REGPARM
 #endif
 
-#if __GXX_WEAK__
 // Declare all libitm symbols we rely on, but make them weak so that we do
 // not depend on libitm.
 extern void* _ZGTtnaX (size_t sz) __attribute__((weak));
@@ -213,19 +219,6 @@ extern void _ITM_memcpyRnWt(void *, const void *, size_t)
 extern void _ITM_addUserCommitAction(void (*)(void *), uint64_t, void *)
   ITM_REGPARM __attribute__((weak));
 
-#else
-// If there is no support for weak symbols, create dummies.  The exceptions
-// will not be declared transaction_safe in this case.
-void* _ZGTtnaX (size_t) { return NULL; }
-void _ZGTtdlPv (void*) { }
-uint8_t _ITM_RU1(const uint8_t *) { return 0; }
-uint32_t _ITM_RU4(const uint32_t *) { return 0; }
-uint64_t _ITM_RU8(const uint64_t *) { return 0; }
-void _ITM_memcpyRtWn(void *, const void *, size_t) { }
-void _ITM_memcpyRnWt(void *, const void *, size_t) { }
-void _ITM_addUserCommitAction(void (*)(void *), uint64_t, void *) { };
-#endif
-
 }
 
 // A transactional version of basic_string::basic_string(const char *s)
@@ -441,3 +434,5 @@ CTORDTOR(14overflow_error, std::overflow_error, runtime_error)
 CTORDTOR(15underflow_error, std::underflow_error, runtime_error)
 
 }
+
+#endif  // _GLIBCXX_USE_WEAK_REF